SOLUTION: How many liters of pure water must be added to 40 liters of a 30% alcohol solution to make a 20% alcohol solution? I have tried X+40(.3)=.2(40+X) but i keep getting it wrong.

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Question 725387: How many liters of pure water must be added to 40 liters of a 30% alcohol solution to make a 20% alcohol solution?
I have tried X+40(.3)=.2(40+X) but i keep getting it wrong.

Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
+.3%2A40+=+12+ liters of alcohol in solution
Let +w+ = liters of water to be added
+12+%2F+%28+40+%2B+w+%29+=+.2+
+12+=+.2%2A%28+40+%2B+w+%29+
+12+=+8+%2B+.2w+
+.2w+=+4+
+w+=+20+
20 liters of water should be added
check:
+12+%2F+%28+40+%2B+w+%29+=+.2+
+12+%2F+%28+40+%2B+20+%29+=+.2+
+12+%2F+60+=+.2+
+12+=+.2%2A60+
+12+=+12+
OK